Devices for monitoring fluid flow and pressure in a hydraulic system and responding to pressure and flow transients that immediately follow a ruptured hydraulic line, hose or hydraulic device leak, so-called “hydraulic fuses,” are known in the art. Hydraulic fuses are typically in-line valves that protect a hydraulic system or subsystem by sensing increased flow through the valve, resulting from a rupture line or leak, and closing the valve to block fluid flow upstream of the rupture to prevent further spillage.
While hydraulic fuses adequately protect a hydraulic system from fluid loss, they are generally incapable of protecting a hydraulic system from over-pressurization. To prevent over-pressurization, hydraulic systems or subsystems typically include a burst disk, pressure relief valve or other pressure relief device. While these devices effectively vent pressurized fluid when a hydraulic system or subsystem is over-pressurized, they exhibit a number of limitations. Among other limitations, burst disks must be replaced once they are ruptured. Additionally, unlike in-line hydraulic fuses, burst disks require additional plumbing for discharging pressurized fluid. Another limitation of burst disks is that they expose a downstream portion of the hydraulic system to a momentary high-pressure impulse prior to and during rupture. Moreover, burst disks have a tendency to fail due to low-pressure cycling fatigue.
Like burst disks, pressure relief valves also require additional plumbing for fluid discharge and expose a downstream portion of the hydraulic system to a momentary high-pressure impulse prior to the valve opening. Another limitation of pressure relief valves is that they are relatively large in size and weight, rendering them unsatisfactory for use in hydraulic systems where size and weight must be minimized.
For at least these reasons, a need exists for a relatively small and lightweight, in-line hydraulic device that monitors static and dynamic fluid pressure in a hydraulic system or subsystem and closes virtually instantaneously upon detection of an over-pressure condition to prevent a portion of the hydraulic system downstream of the valve from being exposed to the over-pressure condition and any associated pressure impulse. Moreover, a need exists for an in-line hydraulic device that automatically reopens when the over-pressurized condition returns to a safe pressure condition.